current_users = ['Hailun','Jeke','Eric','Admin','John','Heel']
new_users = ['jieke','hailun','pairwan','john','kijie']

current_users1 = [current_user.lower() for current_user in current_users]  #转换为小写
new_users1 = [new_user.lower() for new_user in new_users]
print(current_users1)
print(new_users1)

for new_user in new_users1:              #检查两个列表有没有相同用户名
    if new_user in current_users1:
        print(new_user+" in ")
    else:
        print("not in")

for new_user in new_users1:
    if new_user in current_users1:
        print(new_user.title()+".You need to enter another user name.")
    else:
        print(new_user.title()+".This username is not in use.")